CBS Radio, Inc., formerly known as Infinity Broadcasting Corporation, is one of the largest owners and operators of radio stations in the United States, third behind main rival Clear Channel Communications (which owns many of the stations that were previously owned by former CBS parent Viacom before 1997) and Cumulus Media. CBS Radio owns around 130 radio stations across the country. It is currently part of CBS Corporation, which also owns the CBS radio and television networks, and jointly owns the CW Television Network.

CBS Radio is one of the oldest units within CBS Corporation, second to the CBS Radio Network, and has been around since 1928. The CBS Radio Network, however, was launched in 1927, when CBS itself was known as United Independent Broadcasters. Columbia Records later joined in and that company was renamed the Columbia Phonographic Broadcasting System. In September 1927, Columbia Records sold the company to William S. Paley and in 1928, Paley streamlined the corporate name to Columbia Broadcasting System.

CBS Broadcasting Inc. (CBS) is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. It is the second largest broadcaster in the world behind the BBC. The network is sometimes referred to as the "Eye Network" in reference to the shape of the company's logo. It has also been called the "Tiffany Network," which alludes to the perceived high quality of CBS programming during the tenure of its founder William S. Paley (1901–90). It can also refer to some of CBS's first demonstrations of color television, which were held in a former Tiffany & Co. building in New York City in 1950, thus earning it the name "Color broadcasting system" back when such a feat was innovative.^{[citation needed]}

The network has its origins in United Independent Broadcasters Inc., a collection of 16 radio stations that was bought by William S. Paley in 1928 and renamed the Columbia Broadcasting System. Under Paley's guidance, CBS would first become one of the largest radio networks in the United States and then one of the big three American broadcast television networks. In 1974, CBS dropped its full name and became known simply as CBS, Inc. The Westinghouse Electric Corporation acquired the network in 1995 and eventually adopted the name of the company it had bought to become CBS Corporation. In 2000, CBS came under the control of Viacom, which coincidentally had begun as a spin-off of CBS in 1971. In late 2005, Viacom split itself and reestablished CBS Corporation with the CBS television network at its core. CBS Corporation is controlled by Sumner Redstone through National Amusements, its parent.

Radio is the transmission of signals through free space by electromagnetic waves with frequencies significantly below visible light, in the radio frequency range, from about 3 kHz to 300 GHz. These waves are called radio waves. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space.

Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

The etymology of "radio" or "radiotelegraphy" reveals that it was called "wireless telegraphy," which was shortened to "wireless" in Britain. The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, a description provided by the French physicist Édouard Branly in 1897. It is based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray").